The prostaglandins are C-20 unsaturated fatty acids which exhibit diverse physiological effects. The prostaglandins of the E-series are those which have at the nine position a carbonyl group and a hydroxy function at the eleven position.
The prostaglandins of the E-series are potent vasodilators (Bergstrom et al., Acta Physiol. Scand. 64:332-33, 1965 and Life Sci. 6:449-455, 1967) and lower systemic arterial blood pressure on intravenous administration (Weeks and King, Federation Proc. 23:327, 1964; Carlston et al., Acta Physiol. Scand. 75:161-169, 1969). Another well known physiological action for PGE.sub.1 and PGE.sub.2 is as a bronchodilator (Cuthbert, Brit. Med. J. 4:723-726, 1969).
Still another important physiological role for the natural prostaglandins is in connection with the reproductive cycle. PGE.sub.2 is known to possess the ability to induce labor (Karim et al., J. Obstet. Gynaec. Brit. Cwlth. 77:200-210, 1970), to induce therapeutic abortion (Bygdeman et al., Contraception, 4:293, 1971) and to be useful for control of fertility (Karim, Contraception 3:173, 1971). Patents have been obtained for several prostaglandins of the E-series as inducers of labor in mammals (Belgian Patent 754,158 and West German Patent 2,034,641).
Still other known physiological activities for PGE.sub.1 are in the inhibition of gastric acid secretion (Shaw and Ranwell, Worcester Symposium on Prostaglandins, New York, Wiley, 1968, p. 55-64) and also of platelet aggregation (Emmons et al., Brit. Med. J. 2:468-472, 1967).